Carrier signal system



June 11, 1929.

H. B. ARNOLD I 1,717,083 CARRIER SIGNAL SYSTEM Filed Feb. 29. 1928 2 Sheets-Sheet 1' I mm/vlsy June 11, 1929. H. s. ARNOLD CARRIER SIGNAL SYSTEM Filed Feb. 29, 1928 2 Sheets-Sheet 2 QEQEQ mu eum 11,1929.

- UNITED STATES HENRY}. ARNOLD, OF NEW YORK, N. Y., TOBIES, INCORPORATED, 01* NEW YORK, N. Y.,

To BELL TELEPHONE muons- A. cosronarron or new YORK.

ASSIGNOB CARRIER "SIGNAL SYSTEM.

Application filed. February 29, 1s2a. Serial m. 257,se4.'

' lines.

One object or: this invention is to provide a power line carrier signaling system having a number of signal stations connected to a power line and an extension station connected to one of the signal stations by unexposed conductors which serve for calling and signalling so that selective calling and communication may he efiected between the extension station and the signal stations.

Another object of my invention is to provide a powerdine carrier telephone system of the above indicated character having an extension station connected to one of the signaling stations onthe power line that shall provide means whereby the extension station may call and communicate with the associated'signal station or operate apparatus at the associated signal station to selectively call and communicate with any other signal station.

In power-line carrier-current telephone systems now in service, a number of signal stations are connected to a power line carrying low frequency power currents so that high frequency carrier waves may be used to,

transmit signals over the power line.

The application of IV, V. Wolfe, Serial No. 664,147, filed September 22, 1923. Patent 1,678,133, patented July 24, 1928, discloses a carrier wave signaling system whereby telephoning over high voltage power lines may be effected with safety to the operators and the signaling apparatus. In that system, any of a plurality of signal stations may freely call and converse with any other station on the line. Calling is accomplished,

for example, by transmitting impulses on the lower of two carrier frequencies, aselector at the called station responding to a predetermined code of impulses. Each station is provided with a high pass and a low pass filter for passing waves of one frequency and suppressing waves of the other frequency. The high pass filter at each station is normally connected to the outgoing channel blind the ,low pass filter is normallyconnected to the incoming channel. Arelay arrangement is employed to interchange the filters wlth re spect to the incoming and outgoing channels whereby the station originating a call transmits on the lower of the two frequencies and receives on the higher frequency.

The signal stations in systems similar to those disclosed in the Wolfe application are located adjacent to the power line. In many cases, however, it is desirable to communicate over the power line from apoint located away from t for example, may desire a station located at his home or the ofiicials of the power company may desire stations at oflices located away from the powerline.

The present invention provides means whereby an extension station located away from the power line is so connected to a sig nal station on the powerline as to permit calling and conversing between the extension station and any of the signal stations connected to the ower line. The extension station is provi ed with means for controlling the carrier current apparatus at the associated signal station selectively to call and converse with the signal stations connected to the power line, and to call and converse with the signal station associated therewith.

Furthermore, a signal station connected to the power line may selectively call and converse with any other signal station on the power line and call and converse with the extension station or the signal station associated with the extension station.

The extension station may be connected to the associated signal station either by a two wirev circuit or by a four wire circuit. The extension circuits are not exposed to the influence of the power lines so that direct current control of the apparatus at the associated signal station from the extension station may be effected over the connecting wires used for signaling and reduce the amount of control apparatus required. Moreover, the communication between the extension station and the associated signal station may be eftransmitting channel at the associated signal station. In case conversation takes place between the extension station and the associated signal stations, means are provided antomatically to reverse the two pairs of connecting wires at the associated signal station upon removal of the receivers at the extension station and the associated signal station from their switchhooks.

In the accompanying drawings Figure 1 is a diagrammatic view of a power line communication system constructed according to the invention and having a four wire conncction between an extension station and a signal station on the power line.

Fig. 2 is a'diagrannnatic view of a modification of the system shown in Fig. 1 and discloses a system havlng a two wire connection between the.extension station and a signal station on the power line.

Referring to Fig. 1 of the drawings, a power-line carrier-current communication system is shown comprising a power line 1 having carrier current signal stations A and B connected thereto. It is to be understood that other similar carrier current signal stations are connected to the power line at distant points. Each signal station is equipped with terminal apparatus substantially similar in arrangement and function to that shown at station B. The station B has some addi tional apparatus for control from an extension station. An extension station C is connected to the signal station B by means of four conductors 2, 3, 4 and 5.

The signal station B comprlses a transmitting channel D and a receiving channel E.

. The transmittting channel .D comprises a 'modulator 6, an oscillator 7, and an amplifier 8. The frequency of the current generated by the oscillator 7 is controlled by a relay 9 which in the operated position connects a condenser 10 in shunt to a condenser 11 in and receives at a higher carrier frequency.

The called station receives at the low carrier frequency and-transmits at the higher carrier frequency. Normally, each station is positioned to receive at low frequency and to transmit at high frequency. The frequency of the current at the calling station is controlled by means of the above mentionedrelay 9.

The receiving channel E at station B comprises-an amplifier 12 and a rectifier 13.-

ormally the receiving channel E is connected to the power line 1 through a gain con- "trol device 14, a low pass filter 15 and a coupling filter 16. The transmissi n cha nel channel when the station is operating as a calling stattion. A selector 20 of the type shown in patents to J. C. Fields No. 1,200,095 dated October 6, 1916 and 'No. 1,343,256 dated June 15, 1920, is provided for operating a calling signal either at the carrier current station B or at the extension station C.

Call from extension station (F ig. 1

In calling a distant station from the extension station C the receiver at the extension station is removed from the switchhook for completing a circuit to operate a relay 21 at the extension station. The relay 21 is energized from a battery 22 through a switch member23 controlled by the switchhook. Relay 21 operates the switch member 24 for completing a circuit from battery 25 through a relay 36. The circuit for relay 36 extends from battery 25 through one winding of a retard coil 37, one winding of the relay 36, switch member 24, secondary winding of the transformer 38. lower winding of the relay 36, lowerwinding of the retard coil 37 and ground to the battery 25. The relay 36 operates one switch member 39 for preparing a circuit to operate a relay 40. The relay 40 is only operated when the extension station C calls the associated carrier current signal station B. In the case under consideration we are assuming the extension station is calling a distant carrier current signal station. A second-switch member 40 is operated by the relay. 36 for completing a circuit to operate a relay 41 and a relay 42. The relay 42 serves to connect battery to the filaments of the tubes included in the transmission channel D. The relay 41 operates one switch member 43 for completing a circuit through an armature of a relay 44 to operate the relays 18 and 19 that control the connections of the high pass filter 17- and the low pass filter 15 to the transmission channel D and the receiving channel E. Thus the relays 18 and 19 are operated to connect the transmission channel D to the powerline 1 through the low pass filter 15 and to connect the receiving nal desired to transmit to the distant station. 7

The key SK closes a circuit forpulsing a relay 45, The circuit fonoperating the pulsing relay 9 to release this relay and also to effect.

being transmitted to prevent transmission of the code si nal to the receiver at the extension station. The pulsing relay operates a switch member 51 for controlling the relay 9 which in turn controls the frequency of the carrier current generated by the oscillator 7 in the transmission channel D. The relay 9 is normally operated by means of a circuit extending from ground through the coil of the relay 9, resistance 52, relay 53 and battery 54 to ground. The relay 9 is a low current relay and is operated by very little current whereas the relay 53 is a high current relayand takes considerable current to effect operation thereof. Thus, normally the battery 54 supplies suflicient current through the coil of the relay 53 and the resistance'52 to effect operation of the relay 9 but not to effect operation of the relay 53. \Vhen switch member 51 of the relay 45 is operated a shunt circuit is connected around the coil of the operation of the relay 53. The relay 9 and the relay 53 are released and operated in accordance with the operation of the pulsing relay 45which is controlled by the key SK.

The relay 9 controls the transmission of im-- pulses of the lower frequency current which 1S transmitted over the power line to the various signal stations. The relay 53 controls the operation of the selector 20 and if a code signal had been transmitted for calling the associated siganl station B a circuit would have been completed through the contact member 55 for operating the call bell 56 at the signal station B.

Operation at called station (Fig. 1) l Inasmuch as the low pass filter 15 is connected to the transmission channel D at the callingstation only low frequency impulses are transmitted over the line 1. The low frequency impulses are received at the called station through a coupling filter 16 and a low pass filter which at the called station is connected to the receiving channel. The transmitting and receivin channels at all the signal stations connecte to the power line are similar in construction and accordnal at a distant pass filter 17 is connected to the transmission channel D. The impulses of low frequency current, which are transmitted through the coupling filter-of the low pass filter 15 are amplified by the amplifier 12 and rectified by the rectifier 13. Such rectified impulses are of suflicient strength to effect operation of a marginal relay 57. The marginal rela in turn efi'ects operation of the relay 44 w lich operates a switch member 58 for completing a circuit tooperate the selector 20. The selector 20 in the manner disclosed in the above mentioned application of W. V-. Wolfc completes a circuit for operating an alarm. For a more detailed description of thee eration of the transmitting channel D an the receiving channel E reference may he had to the above mentioned application of W. V.

Gall from carrier signal station (Fig. 1)

If the associated carrier current station B desires to call either a distant station or the associated extension station C the key SK is operated in the same manner'as the key SK for directly controlling the operation of the relay 9. lhe operation of the relay 9 by the key SK for calling a distant station is the same as was described with reference to key SK. However, when the key SK is operated to call the associated extension station C the selector 20 is operated tor completing a circuit through the contact member 60 to effect operation of the relay The relay 47 upon operation completes a circuit for operating a relay 61 whie in turn completes a circuit from the battery 22 for operating the bell 62 at the extension station.

WVhen the carrier-current signal station B calls extension C or extension station C calls the carrier-current station B communication is eflected between the two stations at audiofrequency over the conductors 2, 3, 4 and 5. When the receiver at the station B is removed from its switch hook and the receiver at the extension'station C is removed from its switch hook a circuit is completed from a battery 63 for operating the relay 40. Upon operation of the relay .40 it will be noted that the connection of the transmitter and the receiver to the conductors 2, 3, 4 and 5 is reversed so that the transmitter at station B is connected to the receiver at station C and the receiver at station B is connected to the transmitter at station C. Under normal conditions the transmitters at the stations Band C are positioned to be connected to the carrier current transmission ehannel D and the receivers are positioned to be connected to the receiving channel E.

' The communication circuits between the extension station 0 and the transmission channel D and the receiving channel E are completed over the lines 2, 3, 4 and 5 through the condensers 70. A ra sformer 71 is procarrier current vided for connecting transmitters at the stathe retardation coil 37have balanced Windings and offer a high impedance to currents of talking frequencies. Moreover, the pulsing relay 45 has balanced'windings and a laminated core to offer high impedance to currentsoftalking frequencies and prevent interference with the communication circuits.

Calling from dista-atstation. (Fig. 1).

In case a call is received from a distant station on thepower line 1 for the extension station C impulses of the lower frequency are received through the coupling filter 16, the low pass filter 15, amplifier l2 and the rectifier 13 which has its space current increased to a point suflicient to operate the marginal relay 57. The marginal relay 57 operatesthe relay 44 which completes a circuit for operating a selector 20. The selector 20 completes a circuitthrough the contact member 60 for operating the relay 47. The relay 47 starts the operation of the bell 62 in'the manner above set forth in describing a call from the station B to the station C. In case the call from the distant station isfor the signal station B the selector 20 completes a circuit through the contact member 55 for operating the bell 56. Upon receipt of a call at the extension-station C the operator removes his receiver from the switch hook and completes a circuit through the battery 22 for operating the relay 21. The

relay 21 opens the circuit of the relay 61.to.

stop operation of thebell 62 and also for completing the communication circuits to .th transmitting channel D. Two 'wire extension circuit (Fig. 2) Referring to F ig. 2 of the drawings a modification of the system shown in Fig. 1 is illustrated wherein the extension station C is connected to the carrier-current signal station B by means of a two-wire line. Inasmuch as the system shown in Fig. 2 uses substantiallythe same apparatus as shown in Fig.1 and as the transmission channels and receiving channels are similar, like parts will be: indicated by similar reference characters.

Call from extension station .(Fig. 2)

' 73 through one coil of the relay 72, upper switch member of a relay 74, armature of the relay 75, retard coil 76, switch member 71 operated by the receiver switch hook, lower switch member of-the relay 74 and another winding of the relay 72 through ground to the battery 7 3. The normally closed circuit for the relay 72 through a polarized relay 88 does not permit suflicient current flow to operate the relay 72. The-relay 72 upon operation com letes a circuit from a battery 77 for operatinga relay 78. The winding of the relay 78 is shunted by resistances 79 and a condenser 80 in order to permit quick operation of the relay and a slow release thereof. The relay 78 in turn operates a relay 81. The relay 81 operates a switch member '82 for completing circuits to/operate the relay 42 and the relay 41. The relay 42 as above set forth in describing the system shown in Fig. 1 coin trols the so ree of heating current for the discharge devices in the transmission channel D. The relay 41 operates the switch member 43 for completing a circuit to effect operation of the filter relays 18 and 19. The filter relays interchange the connections of the filters 17 and 15 so that the transmission channel D is connected to thepower line through the low pass filter, and the receiving channel E is connected to the power line through the high pass filter 17. The key SK, which is similar to the key SK at the extension station shown in the system of Fig. -1, is operated for sending selected signal impulses of low frequency current over the power line l'to operate the selector at the distant station. The key SK operates the relay, which opens and closes the circuit above traced for operating the relay 72. When the relay 72 is released a shunt ground circuit is connected around the relay 9 which controls the oscillator 7 in the manner above setforth in discussing the system shown in Fig. 10f the drawings. Normally,

as above set forth, the relay 9 which is a low current relay, is operated by current supplied from the battery 54 through-the relay 53 and the resistance 52. The relay 53, which requires a greater amount of current to effect its operation, is not operated by the current which efi'ects operation in relay 9. Consequently, under normal conditions the relay 9 is in operated condition and the relay 53 is in released condition. Therefore, the shuntcircuit completed by the relay 72 around the winding of the relay 9 serves to release the relay 9 to position the oscillator 7 for generating current of high frequency. Upon operation of the relay 9 the frequency of the current generated by the oscillator 7 is reduced.

Consequently by operating the key SK the relay 9 is intermittently operated to transmitimpulses of low frequency over the line 1 for operating the selector at the distant station. The relay 78 which is a slow release relay is not released during the intermittent operation of the relay 72 during the calling operation. Accordingly, the relays 81 and 41 are .held in closed position and also the relays 18,

19 and 42. The relay 72 hasa laminated core in order to offer high impedance to currents of talking frequencies and condensers 84 are provided in the circuit between theextension circuit and the channelsD {and E to permit thefiow of s flow ofthe direct current used inithe Control circuits. The transmission channel-l) and the receiving channel E are connected to" the transmitter and receiver at station C for communication purposes by means of a hybrid coil 85.

If the associated carrier current signal station B is called in place of a distant carrier current signal station the selector 20 is operated to complete a circuit through the contact member 55 for operating the signal bell 56. Upon removal of the receiver from the switch hook of the carrier current station B communication between stations B and C may be effected by currents of audio-frequency:

Call from distant station (Fig. 2) If adistant station calls the extension station 0 impulses of the lower frequency are transmitted over the power line for operating the marginal relay 57 in the manner above set forth in describingthe system shown in Fig. 1. The relay 57 operates. the

relay 44 which in turn operates the selector relay 53. The selector completes a circuit throu h the contact member for operating the re lay 74. The relay 74, u on operation, completes a circuit from the hatte 87 for operating the polarized relay 88. The polarized relay 88 is positioned so as not td be operated by the current from battery 73 which operates the relay 72. The relay 88 closes a bell circuit at station C in series with the compensating resistance 89. across the circuit operating the relay. The bell circuit in parallel with the winding of the relay 88 permits a flow of current through the winding of the relay well' above its operating value. The resistance 89 is provided to adjust the current flow through the bell circuit. When the call is answered. by removing the receiver from the switch hook the circuit for operating the relay 88 is opened to stop operation of the bell. ,The relays 72, 78 and 81 are above setforth in describing the operation of acall from the extension station. However, inasmuch as the relay 44 is held in an operated position by the current from the calling station-no circuit can be completed for operating the filter relays 18 and 19. Accordingly, the extension station which is operating as a called station will transmit by means of current'of the higher frequency and receive by means of current of the lower frequency.

In each of the above described systems it will be noted the extension station may call and communicate with the associated carrier current station or any other station on the power line. Moreover, any station on the peech currents and prevent thepower line adapted then operated in the mannerpower line may selectively call any other station or the extension station as desired.

Modifications in the systems and in the arran ment and location of parts may be ma ewithin the spirit and scope of the invention and such modifications are intended to be covered by the appended claims.

What is claimed is:

1. A transmission system. comprising a transmission of power currents and signal waves, signal stat lons connected to said power l1ne,'means for one station to selectively call another, station and to effect communlcationtherewith, an extension station, conductors for connecting theextension station to one of said power line stations to permit calling and ,signaling over the same conductors, .and means operated at said extension station through the associated signal station for selectively calling the power line stations and for-communicating therewith.

2. In a transmission system, a power line for vtransmittin high tension power currents, signal statlons connected to said power line, means at said signal stations for calling and signaling over said power line by carrier current waves, an extension station, conductors for connecting 'said extension station to one of said signal stations to permit callin and signaling over the same conductors, and means operated at said extension station through the associated signal station for selectively calling and signaling said. signal stations connected to the power line. a

3. In a transmission system, a power line for transmitting high tension power currents and carrier wave signal currents, signal stations connected to said power line, means comprising carrier current transmitting and receiving apparatus at each of said signal stations for selectively calling and for effectin extension station, conductors for connecting said extension station to one of said signal stations to permit calling and signaling over the same conductors, and means at said extension station for calling and communicating with the'associated signal station and for controlling the carrier current transmitting and receiving apparatus at the associated signal station to selectively call and signal the various signal stations.

4. In a transmission system, a power line for transmitting high tension power currents and carrier wave signal currents, signal stations connected to said power line, an extension station, conductors for connecting said extension station to one of said signal stations to permit calling and signaling over the same conductors, carrier current transmitting and receiving apparatus at each of said signal stations, tion for controlling said carrier current ap-' paratus to selectively signal and effect telefor the simultaneous communication between stations, an

means at each signal stafecting telephone communication therewith,

,an extension station, conductors for connecting the extension station to one of said signal stations to permit calling and signaling over the same. conductors, means controlled by signal stations connected to the power line for operating the carrier current apparatus at the signal station associated with the extension station to selectively call either the extension station or the signal station associated therewith, and means operative upon removal of the receiver at the extension station from the switch hook for preparing the carrier current apparatus at the associated signal station for telephone communication between the extension station and signal stations.

6'..In a power line carrier telephone system, a power line forctransmitting high tension power. currents and carrier wave signal currents, signal stations connected to said power line, means at said signal stations,

for calling and signaling over said power dine by carrier current waves, an extension station, conductors for connecting the ex- 0 tension station to one of said signal stations to permit calling and signaling over the same conductors, direct current control means between the extension station and the associated signal station for selective calling and for preparing the circuits for telephone communicatiomand means for maintaining the opposite sides of circuits between the extension station and the associated signal station at nearlyzthe same potential with respect to ground.

7 In a transmission system, a power line for transmitting high tension power currents and carrier wave signal currents, signal stations connected to saidpower line. an

extension station having a two wire receiver connection and two wire transmitter connection to one of said signal'stations, means comprising carrier current transmitting and receiving apparatus at said signal stations for efiectingselective calling and telephone communication between the signal stations, meansfor signal stations on the power line to call and effect telephone communication with the extensionstation through the signal station associated therewith, and means'at the extension station to selectively call and efi'ect telephone communication with said signal stations.

' 8. In a power line carrier telephone system, a power line, signal stations connected to said line and having carrier current apparatus for calling other stations and for eflecting telephone communication between stations, an extension station having a two wire receiver connection and a two Wire transmitter connection to one fof said signal stations, means operative upon removing the receiver at the extension station from the switch hook for preparing the carrier current apparatus at the associated signal station to relay a selective call from the extension station to other signal stations and to permit telephone rier current apparatusto efiect selective callg between the signal stations and the extension station. a I

9. In a power line telephone system, a power line, signal stations connected to said'line and having carrier current apparatus r'or calling other stations and for effecting telephone communication between stations, an extension station-having a two wire receiver connection and a two wire transmitter connection to one of said signal stations, means controlled from the extension station for calling and for eflecting telephone communication with the signal stations, and means for automatically reversing the transmitting and 'receivercircuit connections between the extension station and the associated signal station when the receivers at the two stations are both removed from the switch hooks.

In witness whereof, I hereunto subscribe my name this28th day of February. 1928.

' HENRY B. ARNOLD.

DISCLAIMER I ,7

1,717,083.-Henry B. Arnold, New York, N. Y. CARRIER SIGNAL SYSTEM. Patent dated June 11, 1929. Disclaimer. filed February 6, 1930, by the assignee, Bell Telephone'Laboratories, Incorporated.

Hereby enters this disclaimer to the said claims of said Letters Patent which are in the following words to wit:

1. A transmission system comprising a power line adapted for the simultaneous transmission of power currents and signal waves, signal stations connected to said power line, means for one station-to selectively call another station and to effect communication therewith, an extension station, conductors for connecting the extension station to one of said power line stations to permit calling and signaling over the same conductors, and means operated at said extension station through the associated signal station for selectively calling the power line stations and for communicating therewith. v

2. In a transmission system, a power line for transmitting high tension power currents, signal stations connected to said power line, means at said signal stations for calling and signaling'over said power line by carrier current waves, an extension station, conductors for connecting said extension station to one of said signal stations to permit calling and signaling over the same conductors, and means operated at said extension station through the associated signal station for selectively calling and sig-.

naling said signal stations connected to the power line.

3. In a transmission system, a power line for transmitting high tension power currents and carrier wave signal currents, signal stations connected to said power line,

means comprising carrier current transmitting and receiving apparatus at each of said signal stations for selectively calling and for effecting communication between stations, an extenslon statlon, conductors for connecting said extension station to one of said signal stations to permit calling and signaling over the same conductors, and

means at said extension station for calling and communicating with the associated signal station and for-controlling the carrier current transmitting and receiving.

apparatus at the associated signal'station to selectively call and signal the various signal stations.

4. In a transmission system, a power line for transmitting high tension power currents and carrier wave signal currents, signal stations connected to said power line, an extension station, conductors for connecting said extension station to one of said signal stations to permit calling and signaling over the same conductors, carrier current transmitting and receiving apparatus at each of said signal stations, means at each signal station for controlling said carrier current apparatus to selectively signal and effect telephone-communication with any other signal station, means at said extension station for operating the carrier current apparatus at the associated station to selectively call and to effect telephone communication with the other signal stations, and means for effecting telephone communication between the extension station and the associated signal station independently of the carrier apparatus at the associated signal station.

5. In a power line carrier telephone system, a power line, signal stations connected to said line and having carrier current apparatus for calling other stations and for effecting telephone communication therewith, an extension station, conductors for connecting the extension station to one of said signal stations to permit calling and signaling over the same conductors, means controlled by signal stations connected to the power line for operating the carrier current apparatus at the signal station associated with the extension stationto selectively call either the extension station or the signal station associated therewith, and means operative upon removal of the receiver at the extension station from the switch hook for preparing the carrier current apparatus at the associated signal station for telephone communication between the extension station and signal stations.

[Ojicial Gazette February 25, 1.980.] 

